The invention relates to a production unit, in particular a bending press for shaping workpieces of sheet metal between two press beams equipped with bending tools which can be displaced relative to one another by means of a drive system and incorporating a control unit.
Production machines such as edging presses for bending sheet metal workpieces are fitted with various known safety features to prevent accidents, such as can occur if a machine is not operated correctly, by means of which the working area in the immediate vicinity and between bending tools which move relative to one another in order to perform a work process is protected, so that an emergency stop can be operated if body parts of an operator happen to be in this protected area. One such feature known from the prior art is a “light curtain” for example whereby a beam emitter emits light beams to an oppositely lying beam receiver and the machine is stopped if the light beam is interrupted. Many such machines are also fitted with a “two-hand control” by means of which the operator must use both hands to operate separate switches or control buttons simultaneously in order to initiate the forming process, which is a reliable means of ensuring that the hands are not in the working area. However, a system of this type does not offer any protection for any person present who is not directly involved in operating the machine or against manipulation of the safety system.
A production unit is known from patent specification DE 100 00 287 A1, in particular a bending press for shaping workpieces of sheet metal between press beams equipped with tools that are displaceable relative to one another by means of a drive system. A control system has a detection system and at least one detection means which is connected so as to communicate with the detection system in order to transmit data and/or signals, in which an analysis-control module is provided, as well as a data memory. The detection means of the detection system is a camera, by means of which the immediate working area around the displaceable press beam is monitored, and image signals are continuously evaluated so that the production unit can be switched off as soon as pre-defined image patterns indicate that an operator has encroached on the immediate area presenting a risk.
Patent specification DE 196 19 688 A1 discloses a method of monitoring rooms in which machinery is operated by means of video, whereby a video camera is used as the optical detection means to monitor the operating room, and en electronically processable image of the free operating room is generated and transmitted from the camera to an image processor, where it is stored. Whenever the press is switched on, the video camera records another image of the operating room and the image processing system compares the generated image with the stored image. The press can not be operated unless the new image is identical to the stored image.
Document U.S. Pat. No. 5,081,406 A discloses a monitoring and control system for operating a machine with power-operated tools, for example a saw blade, and has a system for protecting an operator. A control and monitoring system has a detection system, by means of which capacitive changes in the area of the moved tool caused by the approach of an operator are detected and evaluated in a control circuit. If the operator moves dangerously close to the tool and thus causes a variation in the measurement values, the emergency stop of the moved tool is activated.